Study On Preparation And Properties Of Nanoporous Ti-Cu Films On Stainless Steel

Austenitic stainless steels are widely used in food industries, utensils and surgical instruments due to their superior corrosion resistance and workability. However, dust, biological fouling, bacteria, viruses and other harmful microorganisms occur on stainless steel surface. Thus the development of stainless steel with excellent photocatalytic and antibacterial properties is of great significance.Nanoporous metal is one of the most important nanomaterials and widely used in electrochemistry, photochemistry, catalysis, due to its unique structure and property. Exploiting preparation of functional nanoporous metal material, further studying its structure, and exploring its applications are of special significance. In this study, Ti-Cu films were deposited onto AISI 316 L stainless steel substrates by closed field unbalanced magnetron sputtering. And then, the nanoporous Ti-Cu films were obtained by dealloying treatment of Ti-Cu films. At the same time, considering the TiNi alloy has unique shape memory alloy performance, the TiNi films of equal atomic ratio were perpared onto AISI 316 L stainless steel substrates by closed field unbalanced magnetron sputtering. The TiNi films were used to improve the corrosion-wear resistance of stainless steel. Preparation parameters had been optimized to improve the surface properties, such as wear resistance and corrosion resistance, as well as photocatalysis, electrocatalysis and antibacterial properties. X-ray diffraction（XRD）, Scanning electron microscopy（SEM）, glow-discharge optical emission spectroscope（GDOES） and X-ray photoelectron spectroscopy（XPS） were employed to study the structure of films. The electrocatalysis, photocatalysis, antibacterial, wear and corrosion properties of these films were investigated. The results were summarized as follows:（1） The microstructure morphology characteristics of all samples have been analyzed. The Ti-Cu films are homogenous and continuous. Ti-Cu films are mainly composed of Cu₄Ti₃, Cu_0.81Ni_0.19, TiNi_0.8 Cu_0.2 and γ-Fe. The nonporous Ti-Cu films were obtained by dealloying treatment of Ti-Cu films. Ti_31.28Cu_64.71 is mainly composed of Cu₄Ti₃ and Cu₂Ti₄ O.（2） The electrocatalytic activities of nanoporous Ti-Cu modified stainless steel toward ethylene glycol have been studied by cyclic voltammetry. Under the different p H value, the nanoporous Ti-Cu films reveals significantly different electrocatalytic oxidation activities toward ethylene glycol. In alkaline condition, the nanoporous structure can effectively promote the oxidation of ethylene glycol reduction reaction.（3） The photocatalytic performance of nanoporous Ti-Cu films has been studied. The visible light photoactivities of nanoporous Ti-Cu were greatly improved as compared with the undoped TiO₂. Methylene blue aqueous solution degradation rate of nanoporous Ti-Cu films is 1.83 times compared with the undoped Ti O2 under visible light for 6 h.（4） Nanoporous Ti-Cu modified stainless steel possess strong antibacterial effect against Escherichia coli（E. coli） and Staphylococcus aureus（S. aureus）. The antibacterial effect of nanoporous Ti-Cu modified stainless steel against E. coli and S. aureus reaches above 96.7 % and 100 % within 24 hours. Different antibacterial effects attribute to photocatalytic sterilization of Cu-TiO₂ and Cu ions with a good effect on medical sterilization.（5） The tribological properties and mechanism of surface modified stainless steels have been investigated and compared with those of stainless steel substrate. Ti-Cu modified stainless steels can decrease the coefficient of friction sliding against Si₃N₄ ball in Hanks’ solution. The Ti-Cu modified stainless steel shows better corrosion and wear resistance than others in Hanks’ solution.（6） The electrochemical corrosion properties of surface modified stainless steel and stainless steel substrate have been characterized and compared. In simulated human body fluids, Ti-Cu surface modified layers improve the corrosion resistance of stainless steel. According to the surface topography of corrosion, stainless steel has the phenomenon of pitting corrosion. However, the presence of Ti-Cu films can effectively inhibit the formation of pits.（7） The corrosive-wear properties of near-equiatomic Ti Ni films have been investigated. The Ti Ni films effectively improve the corrosion wear resistance of stainless steel in simulated human body fluids. This attributes to formation of the dense SiO₂ and Ti O₂ thin films in the friction process and pseudoelasticity of TiNi films.